1. Field Of The Invention
The present invention relates generally to refrigeration. In a more particular sense, the invention has reference to refrigerated display cases of the type used in food markets. In yet a more specific sense, the invention is a refrigerated display case of the so-called "wide island" category, in which side-by-side product display wells are separated by an upstanding partition that extends longitudinally and centrally of the case, with both wells being uncovered and opening upwardly to provide ready access to the displayed products.
2. Description Of The Prior Art
Refrigerated display cases of the type referred to above require frequent defrosting. To this end, many defrosting arrangements have been utilized in the art. One of these is air defrost. A case utilizing this defrost means draws ambient air into the conduits or air passages through which refrigerated air is circulated during refrigeration cycles. The relatively warm ambient air, when circulated through the conduits, melts the frost that has accumulated on the conduit walls and even more importantly on the evaporator coils, until ultimately the conduits and coils are completely clear of frost and are ready for resumption of the refrigeration cycle.
While air defrost can advantageously be employed in many types of cases, it has certain disadvantages as compared to other defrost arrangements. For example, hot gas defrost is widely used, and is highly efficient in that it accomplishes complete defrost in a relatively short time. Hot gas defrost, however, involves additional piping and valving, and requires special attention to the pressures developed in different areas of the system. Electrical defrost is also well known, utilizing electrical heating elements to melt the frost from the evaporators. The electrical energy requirements of this type of defrost, however, are high.
Considerable efforts, accordingly, have been made to develop efficient air defrost systems for refrigerated display cases, which require no additional piping or valving, and which add only minimally to the normal electrical energy requirements of the case.
Air defrost systems, however, have their own peculiar set of problems, and these problems can vary from one type of case to another. In a wide island case, for example, it is common to design the case for merchandising frozen food along one side of the case, in one product well, and ice cream in the product well at the other side. In such instances, the temperature requirements at the opposite sides of the case differ. Accordingly, during a refrigeration cycle it is important to keep the air circulating around one product well at a given temperature, while maintaining the circulating air of the other product well at a different temperature. Intermixing of the air circulated about one well with the air circulating about the other well, during a refrigeration cycle, should understandably be held to a minimum.
Yet, despite the obvious desirability of preventing commingling of the air flow patterns during refrigeration in wide island cases of the type described, there are strong reasons for defrosting both wells simultaneously and, of course, in the shortest possible amount of time. For example, one reason for simultaneously defrosting both sides of the case is that if one side is maintained in refrigeration while the other side is in defrost, heat exchange between the two sides would adversely affect both the refrigeration of the first side and the defrost of the second side. In any event, the prior art as exemplified by such patents as U.S. Pat. No. 4,314,457 and 4,337,626 both to Ibrahim; 4,304,098 to Rydahl; and 4,182,130 to Ljung, all disclose one or another of two types of wide island cases: (a) "unitized" cases in which there is a center flue that is common to both sides so that both sides must carry the same products to be refrigerated to the same temperature, with the air being intermixed both during refrigeration and defrost; or (b) cases in which the air flows at opposite sides are kept separate both during refrigeration and defrost.
Accordingly, it is desirable that if possible, in a wide island case having a partition down the center rather than a common center flue, and adapted for maintaining different refrigerating temperatures at the respective, opposite sides of the partition, there should be an air defrost system which will, during defrost and only during defrost, draw defrost air from the ambient atmosphere and circulate it through the conduit of one side, and then transfer it to the other side of the case, for circulation through the conduit and evaporator thereof, and then exhaust it back to atmosphere from the conduit of said other side of the case. The present invention has as its main purpose the provision of such a system.